Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h, w = map(int, input().split())
s = [input() for _ in range(h)]
def bfs():
    dist = {(0,0): 0}
    que = deque([(0,0)])
    while que:
        i, j = que.popleft()
        for k,l in ((0,1),(1,0),(0,-1),(-1,0)):
            k += i
            l += j
            if 0<=k<h and 0<=l<w and s[k][l]=='.' and (k,l) not in dist:
                dist[k,l] = dist[i,j] + 1
                que.append((k,l))
    return dist
dist = bfs()
if (h-1,w-1) in dist:
    black = sum(line.count('#') for line in s)
    print(h*w - black - (dist[h-1,w-1]+1))
else:
    print(-1)